The
P-51 Mustang is usually considered to be the best American fighter aircraft of
the Second World War. It had previously undreamed-of range, excellent flying
characteristics, adequate cockpit room and heat for the pilot. It was easily the
equal or better of any enemy airplane.

The genesis of this machine
goes back to 1938 when the British realized that, in the impending war, their
industrial capacity would not be enough to meet their needs. A delegation was
sent to the US to establish a means of augmenting British production. Orders
were placed with LOCKHEED for 200 Hudson bombers and with NORTH AMERICAN
AVIATION for 200 HARVARD advanced trainers. Thus began
a co-operative relationship between the US and England for wartime production.

In 1939, with the invasion of
Poland and the actual declaration of war, the British again approached the
Americans....this time looking for a fighter aircraft. The first choice of the
Brits was the Curtiss P-40, but Curtiss could not deliver anything until the end
of 1940, because of American needs. Pleased with the previous dealings with
North American, the commission approached them about building P-40's under license.
Dutch Kindelberger, the head of the company, suggested that, instead, they
could build a new improved design with increased performance, firepower and
range, using the Allison V-1710-39 powerplant from the P-40. Working
overnight, Kindelberger's design team came up with a sleek new fighter plan by
morning. The British gave the go-ahead to proceed with detailed drawings. On May
29, 1940, an order was placed for 320 of the new aircraft, now designated the
NA-73. The contract required the prototype to be ready within eight months.
North American decided to try for 120 days!

The new design was very
innovative in streamlining techniques....the aircraft was tightly cowled with
only a very small carburetor intake on the topside. The radiator intake was
mounted far back below the wings and was designed for extreme efficiency
regarding drag. The NA-73's armament consisted of a pair of 50 caliber Brownings
in the lower cowling and two 30 caliber Brownings in each wing. The most
important innovation was the decision to use a laminar flow wing design, which
had it's widest part further back than normal....keeping the airflow unbroken
until later, causing much less drag, therefore improving performance, fuel
economy and range.

The prototype was wheeled out
with three days to spare, on August 30, 1940. It wasn't to receive an engine,
however, until October, but the design was seen to be sound and a further 300
machines were ordered. There were the usual teething setbacks but they were
solved and production commenced. The British decided to name the aircraft
"Mustang", to give it an American flavour.

The second production machine
was delivered to England by October 24, 1941.

In tests, the Allison engine,
being unsupercharged, was found to be inadequate at high altitudes. At low
altitudes, it was responsive, stable and was fast in a dive. In light of this it
was decided to use it for close support for the army and for low level photo
reconnaissance. Fighter command, at this time, was developing the Spitfire for
high altitude work.

The Mustang did indeed prove
to be admirably suited to this type of work. The Americans ordered 358 aircraft.
They changed the armament to four 50 caliber Brownings in each wing, dispensing
with the nose guns. They also used a more powerful 1200 horsepower version of
the Allison.

There was also a dive bomber
variant, the A-36A, with dive brakes and other modifications.500 of these were
ordered, but they had problems in action. Ultimately they were replaced by P-47
Thunderbolts.

The Merlin

The
Mustang was seen to be a good airplane, in need of more power. A British test
pilot, impressed by the aircraft, suggested to Rolls-Royce that a Merlin 61 with
a two stage supercharger would greatly enhance the performance. The aerodynamic
engineer at Rolls Royce estimated that 441 miles per hour would be possible at
25,000 feet.

The installation changed the
carburetor intake opening from the top of the cowling to the bottom. By the
second prototype, the speed reached was 433 miles per hour at 22,000 feet. The
improved performance did come at the expense of handling, however, over the
docile Allison versions.

In US versions, the engine
became the Packard built Merlin XX, which attained 453 mph at 28,000 feet, using
war emergency boost....a dramatic improvement over Allison versions. Armament
consisted of either four or six 50 caliber Brownings in the wings. Two
1000 pound bombs or two drop tanks could be carried.

Finally, the allies had a
superb fighter with the range to reach Berlin, so this airplane was used
extensively for bomber escort missions.

The Mustang in all its
versions went on to serve in every theatre of war with distinction. The most
successful of all was the P-51D with its bubble canopy.

After World War 2, the Mustang
soldiered on. A version with two fuselages, the F-82 was used in Korea, along
with regular versions. Many other countries used them for first line defense
well into the fifties, some banana republics continuing on even beyond
this.

To this day, they are favourites in air racing
and warbird gatherings everywhere.